import java.util.Random;

public class Test {

    public static void main(String[] args) {

        Random random = new Random();
        for (int i = 0; i < 30; i++) {
            int g = (int)(30-(Math.random()*60));
            System.out.println(g);
        }
        String ds = "sdfdgadfd";
        //事实会发生下标越界
//        String substring = ds.substring(2, 20);
//        System.out.println(substring);
        int a = 20;
        int b = 3;
        int c = 20 % 3;

    }
}
